1. Field of the Invention
The present invention relates to a method of monitoring and controlling a well pump apparatus. In particular, the present invention relates to a method of monitoring and controlling a well pump apparatus wherein the amount of electricity consumed during reciprocation is measured and wherein statistical analysis techniques are applied to determine optimum fill times, to differentiate between fluid pump-off and gas lock, to determine sucker rod failure or counterweight failure, and to determine motor start failure and transmission belt failure.
2. Prior Art
A typical pumping unit utilizes a pivoted walking beam with a horse head at the outer end. Oscillation of the walking beam produces reciprocal motion of sucker rods and thereby reciprocation of a pump at the bottom of a well.
Oil bearing formations are often in subterranean porous rock or sand. A vertical borehole penetrating such a formation constitutes a relatively small cross-sectional area of the entire crude oil porous formation. Seepage of crude oil from a porous rock or sand formation is a fairly slow process.
For this reason, the typical oil well is pumped in cycles. The well is first pumped for a selected length of time sufficient to pump the fluid accumulated in the well bore to the earth's surface. Once the fluid accumulated in the well bore has been pumped out, a fill time is provided to allow more fluid to seep from the formation into the borehole. As the well ages, crude oil is being drained from greater distances in the producing formation, and longer fill time is required. As fluid migrates through the formation, a fluid level is slowly reached at which equilibrium is established, after which no further fluid flows into the well bore regardless of any additional time allowed.
It will thus be appreciated that it is desirable to know how long the well should be pumped, once pumping action is started, in order to extract the fluid accumulated in the well bore. If the pumping action is stopped prematurely, fluid will be left in the well bore, thereby diminishing the overall production of the well. Conversely, if pumping action continues after the fluid accumulated in the well bore has been pumped to the surface (referred to as a "pumped off" condition) the result is substantially increased wear and tear on the equipment as well as waste of energy required to provide the pumping action.
Accordingly, it is desirous to monitor and control a well pump apparatus so that the pumping cycle is properly terminated when the well is pumped off. Additionally, it is important to accurately determine the optimum fill-time between pumping cycles.
Moreover, it is advantageous to be able to monitor a well pump apparatus to distinguish between a pumped off condition and a gas lock condition.
It is additionally advantageous to be able to monitor a well pump apparatus to detect sucker rod failure.
It is additionally advantageous to be able to monitor a well pump apparatus to detect loss of a counterweight or counterweights so that the apparatus may be stopped and repairs made.
Finally, it is advantageous to be able to monitor and control a well pump apparatus to detect a motor start failure or a loss of the drive belt and to initiate action.